There is a building for left luggage in one of the squares next to the tourist infomation the charge a few euros per day. Your best bet for accomidation if to bring a sleeping bag and sleep in one of the park there a loads of over people doing the same and is quite safe I didnt bring a sleeping bag but I wish I had as it gets surprisingly cold. But be careful of pickpockets as I had my phone stolen and met others that had there trouser slit open as they sleep. There are also public showers to use. If you are running make sure you get to the run before 7am preferably thats when the police close the gates.